The present invention generally relates to data storage devices. More specifically, the present invention relates to removable cartridge storage devices.
Computer backup has traditionally been performed using tape drive technologies. Tape drive technologies have been popular in the use of backup systems for a variety of reasons. One reason is that tape media has generally had the lowest cost per bit of storage. Additionally, tape devices use removable tape cartridges, which may be taken to an off-site location to provide for disaster recovery. A third reason tape devices are popular is because of the long-term archive characteristics of tape media.
Policies may be set by companies specifying requirements for computer system backup for data recover and disaster recovery. One preferred practice requires that multiple copies (typically two) of the data be recorded on magnetic tape or other suitable removable storage medium. One copy is kept on-site for quick access in the event that data must be restored. The other copy is sent off-site for disaster recovery purposes.
System administrators may be faced with a difficult choice when implementing a backup policy that requires multiple copies of data. One solution is to create copies sequentially using a single tape drive. A prior art standalone tape drive that may be used in this type of solution is illustrated in FIG. 1. The tape drive 100 includes a system controller 102. The system controller 102 includes an interface (e.g., Small Computer Systems Interface (SCSI), Fiber Channel (FC), etc.) to a host computer 120 and a microprocessor which performs data formatting for the tape medium. The tape drive 100 also includes a tape recording mechanism 104 which mechanically controls the movement of magnetic tape past the magnetic recording/playback head(s) and magnetically encodes the formatted data on magnetic tape cartridges 106, 108, 110. Tape recording mechanism 104 is also used to read data from the magnetic tape cartridges 106, 108, 110. Although using a single tape drive 100 may minimize cost, the amount of time required for backup is multiplied by the number of copies made. Additionally, as the amount of data stored on the computer systems increases and/or the amount of time available to perform the backup operation (i.e., the backup window) decreases, the ability to perform sequential copies becomes very limited.
FIG. 2 illustrates a second prior art solution that uses multiple tape drives 210, 220 coupled to a host computer system 200. Both tape drives include system controllers 212, 222. Additionally, each tape drive includes a tape recording mechanism 214, 224, which may be used to control the movement of magnetic tape and magnetically encode data on a magnetic tape cartridge 216, 226. Although the two tape drives 210, 220 may be operated in parallel to record the data, this system carries a higher system cost because of the duplication in tape drives 210, 220. Additionally, this system places a larger burden on the network and host computer system 200 as the data must be transmitted twice, once to each tape drive 210, 220.